The invention relates to wax-like polymerizable materials. The invention provides wax-like polymerizable dental materials, and methods of forming dental products of high strength dental polymeric material. This wax-like polymerizable dental material is quickly and easily reshaped. It is reshaped by warming, and shaping while warm and then allowing it to cool to room temperature. The shaped wax-like polymerizable dental material is cured to form dental products. These dental products have superior strength compared to products formed from prior wax-like polymerizable materials. Prior wax-like polymerizable materials do not form strong enough polymeric material for making dentures. High strength dentures are made by positioning artificial teeth in wax-like polymerizable dental material of the invention. The disclosures of U.S. patent application Ser. No. 09/670,364 filed Sep. 26, 2000 now abandoned and U.S. provisional patent application Serial No. 60/237,523 filed Oct. 4, 2000 are incorporated herein by reference in their entirety.
Volkel et al in U.S. Pat. No. 6,057,383 (and Canadian Patent Application 2207351), assigned to Ivoclar, disclose wax-like polymerizable material for making entire dental products. The prior art does not disclose a wax-like polymerizable material for forming dentures or other high strength products.
The invention provides a high strength dental polymeric material formed from wax-like polymerizable dental material. High strength dental polymeric dental products include partial dentures and full dentures.
Working wax-like polymerizable dental material, often includes molding, shaping, and/or carving. When heated, wax-like polymerizable dental material softens. In its softened state, it is believed to be partially crystalline and have a flowable amorphous phase, which allows some flowability of the material. Preferably, wax-like polymerizable dental material is dimensionally stable below 24xc2x0 C. and softened at and above 24xc2x0 C. More preferably it is softened at and above 30xc2x0 C. By heating from its dimensionally stable condition, wax-like polymerizable dental material of the invention undergoes a rapid transition to being freely flowable. By cooling from its softened state, wax-like polymerizable dental material of the invention undergoes a rapid transition to being dimensionally stable. Small volumes of wax-like polymerizable dental material may be worked, while being warmed on the dental device. They may be dispensed from a heated syringe-type dispensing device, spatula, electric spatula, disposal dropper or other mechanical or electrical dispenser. To make a denture, wax-like polymerizable dental material is positioned on a polymeric base plate made from an impression of a patient""s mouth. Artificial teeth are positioned in the wax-like polymerizable dental material, which is then shaped by melting and resolidifying. Then the wax-like polymerizable dental material is polymerized to form a denture. Thus the denture is formed without applying inorganic plaster to the artificial teeth and without positioning artificial teeth in a mold as required by conventional lost wax or other similar prior art methods of forming a denture. Compounds, which are readily partially crystallizable and useful in wax-like polymerizable dental material of a preferred embodiment of the invention, include methacrylate (or acrylate) compounds prepared for example by reaction of a urethane pre-oligomer with hydroxylalkymethacrylate. Preferably such compounds have a structure within the scope of one of general formulas I-V below. Preferably the urethane pre-oligomer is linear, comprises isocyanate end groups and has a structure within the scope of general formula I:
OCNxe2x80x94(R1xe2x80x94NHxe2x80x94COxe2x80x94Oxe2x80x94R2xe2x80x94Oxe2x80x94OCxe2x80x94NH)mxe2x80x94R1xe2x80x94NCO I 
wherein R1 and R2 are either an alkyl having from 1 to 14 carbon atoms or containing at least an aromatic group having from 6 to 14 carbon atoms, m is an integer from 0 to 20, the value of m in the oligomer depends on the molar ratio of diisocyanate to diol used, and the value of m increases as this molar ratio decreases. The diisocyanate portion has the structure OCNxe2x80x94R1xe2x80x94NCO and the diol portion has the structure HOxe2x80x94R2xe2x80x94OH.
Alternatively, urethane pre-oligomer is formed by reaction of at least one diol with excess, at least one diisocyanate to yield a urethane pre-oligomer having a structure within the scope of one or more of general formulas:II-IV
General Formulas: II-IV
wherein R1, Rxe2x80x21, R2 and Rxe2x80x22 each independently is an alkyl having from 1 to 14 carbon atoms or at least an aromatic group having from 6 to 14 carbon atoms, n and m are each independently integers from 0 to 20, the sum of n and m in the oligomer depends on the molar ratio of diisocyanates to diols used, and the value of the sum of n and m increases as this molar ratio decreases. The diisocyanates have the structures OCNxe2x80x94R1xe2x80x94NCO and OCNxe2x80x94Rxe2x80x21xe2x80x94NCO and the diols have the structures HOxe2x80x94R2xe2x80x94OH and HOxe2x80x94Rxe2x80x22xe2x80x94OH. The more complex structures of urethane pre-oligomer are constructed from at least two different diols and at least two different diisocyanates.
Reaction of the urethane pre-oligomer with the ethylenically unsaturated monomer as defined below yields a polymerizable compound having the structure within the scope of the general formula V:CHxe2x95x90C(R3)xe2x80x94CO2xe2x80x94R4xe2x80x94COxe2x80x94NHxe2x80x94(R1xe2x80x94NHxe2x80x94COxe2x80x94Oxe2x80x94R2xe2x80x94Oxe2x80x94OCxe2x80x94NH)nxe2x80x94R1xe2x80x94NHxe2x80x94COxe2x80x94R4xe2x80x94O2Cxe2x80x94C(R3)xe2x95x90CH2V wherein R3 is hydrogen, or an alkyl, such as a methyl group, and R4 is an alkyl group having from 1 to 14 carbon atoms, and n is an integer from 0 to 20. The typical ethylenically unsaturated monomer is a hydroxyalkyl (meth) acrylate, e.g. 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, caprolactone 2-(methacryloyloxy) ethyl ester, etc.
Preferred mechanical properties of cured resin and the adequate handling properties of compositions, polymerizable compound, are present when the value of n in the compound is not greater than 10; more preferably n is not greater than 5. The preferred value of n in the compound largely depends on the requirements of the specific application. The most preferable value of n in the compound for aromatic ring based diol is between 1 and 3. Therefore, the molar ratio of diisocyanate to diol for aromatic ring based diol is most preferable between 1.33 and 2. The most preferable value of n in the compound for alkyl based diol is between 1 and 4. Therefore, the molar ratio of diisocyanate to diol for alkyl based diol is most preferable between 1.25 and 2.
Catalysts known in the art may be used to accelerate the formation of the isocyanate-ended pre-oligomer and end-capped ethylenically unsaturated monomer, for examples, tertiary amines and metal salts, e.g. stannous octoate and in particular dibutyl tin dilaurate. Preferred stabilizers used in this invention are butylated hydroxytoluene (BHT) and the methyl ether of hydroquinone (MEHQ).
Preferably compounds of the invention are difunctional methacrylates including reaction products of bisphenol A propoxylate, 1,6-diisocyanatohexane and 2-hydroxyethyl methacrylate, reaction products of bisphenol A propoxylate, trimethyl-1,6-diisocyanatohexane and 2-hydroxyethyl methacrylate, a series of reaction products of bisphenol A, trimethyl-1, 6-diisocyanatohexane and 2-hydroxylethyl methacrylate, a series of reaction products of bisphenol A, 1,6-diisocyanatohexane and 2-hydroxylethyl methacrylate, a series of reaction products of trimethyl-1,6-diisocyanatohexane, 2,5-dimethyl-2,5-hexanediol and 2-hydroxyethyl methacrylate, a series of reaction products of trimethyl-1,6-diisocyanatohexane, 1,6-diisocyanatohexane, 2,5-dimethyl-2,5-hexanediol and 2-hydroxyethyl methacrylate, a series of reaction products of trimethyl-1,6-diisocyanatohexane, 1,6-diisocyanatohexane, bisphenol A propoxylate and 2-hydroxyethyl methacrylate, caprolactone 2-(methacryloyloxy)ethyl ester, and derivatives of above compounds.
Diisocyanates useful for making wax-like polymerizable dental material of the invention include trimethyl-1,6-diisocyanatohexane, 1,6-diisocyanatohexane, 1,8-diisocyanatooctane, isophorone diisocyanate, 4.4xe2x80x3-methylenebis(cyclohexyl isocyanate), cyclohexyl diisocyanate, 3-methylhexane-1,6-diisocyanate, 3-ethyl-1,6-hexanediisocyanate, 5-methyl-1,9-nonanediisocyanate, 5-ethyl-1,10-decanediisocyanate, 2,3-dimethyl-1,6-hexanediisocyanate, 2,4-dimethyl-1,8-octanediisocyanate, 2,4,6-trimethyl-1,7-heptanediisocyanate, 2,3-dimethyl-5-ethyl-1,8-octanediisocyanate, 2-methyl-4,6,8,10-tetrapropyl-1,12-dodecanediisocyanate and the like, and mixtures thereof. Examples of diisocyanates that are also suitable include aromatic diisocyanates, for example, 4,4-methylene bis(phenyl isocyanate), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,4-phenyl diisocyanate, 1,5-naphthalene diisocyanate, 1,3-bis (isocyanatomethyl)benzene, 1,3-bis(isocyanato-1-methylethyl)benzene, 1,3-bis(isocyanatomethyl)cyclohexane, 3,3xe2x80x3-bitoluene diisocyanate, 1,4-xylylene diisocyanate and the like, and mixtures thereof.
Examples of diols useful for making compounds for wax-like polymerizable dental material of the invention include 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 1,9-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 2,5-dimethyl-2,5-hexanediol, hydrogenated bisphenol A, bisphenol A, propoxylated bisphenol A, ethoxylated bisphenol A, bis (2-hydroxyethyl) terepthalate, and mixtures thereof.
Examples of methacrylates (or acrylates) useful for making compounds for wax-like polymerizable dental material of the invention include 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, hydroxypropyl acrylate, glycerol dimethacrylate, glycerolmonomethacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxycyclohexyl methacrylate, caprolactone 2-(methacryloyloxy)ethyl ester, pentaerythritol triacrylate, 2-hydroxycyclohexyl acrylate and mixture thereof.
Wax-like polymerizable dental material may include one or more initiating systems to cause them to harden promptly. Light curable wax-like polymerizable dental materials preferably include a light sensitizer, for example camphorquinone, Lucirin TPO, or methyl benzoin which causes polymerization to be initiated upon exposure to activating wavelengths of light; and/or a reducing compound, for example tertiary amine.
A room temperature or heat activating catalyst system is preferably included in the wax-like polymerizable dental material of the invention. Preferably included is a peroxide capable of producing free radicals when activated by a reducing agent at room temperature or by heating. Preferred peroxides include benzyl peroxide and lauroyl peroxide.
Wax-like polymerizable dental materials of the invention are believed to rapidly partially recrystallize. This rapid recrystallizability provides a unique combination of free flowability and dimensional stability, depending on its temperature. It is believed that the material rapidly transitions from a freely flowable state by means of rapid crystallization to a dimensionally stable state. The material at solidification temperatures is partially crystalline and the crystallinity present in an amorphous phase results in the effective dimensional stability of the material. xe2x80x9cCrystallinityxe2x80x9d as used herein refers to regularity and order within a material resulting in a heat of fusion of at least 1.0 J/g at and below 50xc2x0 C. Heat of Fusion as used herein refers to enthalpy of fusion as determined by ASTM 793-95. Percent crystallinity is determined by measuring the heat of fusion using differential scanning calorimetry according to ASTM test method E 793-95.
The wax-like polymerizable dental material of the invention is useful for formation of dental products including full dentures, partial dentures, denture liners, custom trays, artificial teeth, repairs for natural teeth, veneers, denture repairs, denture reline, night guards, splints, retainers, orthodontic components, crowns, bridges, provisional dental devices, inlays, onlays, and tooth restorative fillings, orthodontic appliances, oral orthopedic appliances, temporary dentures, temporary partial dentures; maxillofacial prostheses, obturators, and occular prostheses.
Compositions in accordance with the invention may further include fillers, pigments, stabilizers, plasticizers and fibers. Preferably, polymerizable dental compositions in accordance with the invention include from about 2 to about 95 percent by weight filler particles. More preferably, these compositions include from about 10 to about 85 percent by weight filler. Nanocomposites and ceramers may be formed from these composites. The fillers preferably include both organic and inorganic particulate fillers to further reduce polymerization shrinkage, improve wear resistance and modify the mechanical and physical properties.
A preferred embodiment of the invention provides a high strength dental polymeric material formed by light curing wax-like polymerizable dental material shaped into at least a portion of a denture base. Preferably the wax-like polymerizable dental material has a flexural modulus of at least 400,000 psi and a flexural strength of at least 7,000 psi and an un-notched impact strength of at least 2 foot-pounds/inch. Preferably the denture comprises denture base, and a tooth comprising an interpenetrating polymer network polymeric matrix and at least 0.1 percent by weight of self-lubricating particles having a particle size less than 500 microns effectively bonded to and distributed in the polymeric matrix. Preferably the bond strength between the tooth and the denture base is at least 4,480 psi.
xe2x80x9cWax-likexe2x80x9d as used herein refers to material which is flowable (fluid) above 40xc2x0 C., and becomes dimensionally stable (solidifies: i.e. is nonfluid) at least at and below 23xc2x0 C., within 5 minutes. Thus, wax-like material is flowable when it is at and above 40xc2x0 C., and becomes dimensionally stable when it is at and below 23xc2x0 C. Flowable wax-like material having a temperature from 100xc2x0 C. to 40xc2x0 C., becomes dimensionally stable within 5 minutes by cooling by exposure to an ambient temperature between 23xc2x0 C. and 0xc2x0 C. Flowable wax-like material having a temperature from 100xc2x0 C. to 40xc2x0 C., becomes dimensionally stable within (in order of increasing preference) 2, 1, 0.5 or 0.3 minutes by cooling by exposure to an ambient temperature between 23xc2x0 C. and 0xc2x0 C.
xe2x80x9cHigh strength dental polymeric materialxe2x80x9d as used herein refers to material having a polymeric matrix having a flexural modulus of at least 250,000 psi and a flexural strength of at least 5,000 psi. Optionally, high strength dental polymeric material includes reenforcing filler. However, the polymeric matrix alone (without any reenforcing filler) has a flexural modulus of at least 250,000 psi and a flexural strength of at least 5,000 psi. Preferably high strength dental polymeric material has a polymeric matrix having a flexural modulus of at least 300,000 psi and a flexural strength of at least 7,000 psi, and an un-notched impact strength of at least 2 foot-pounds/inch2. More preferably high strength dental polymeric material in order of increasing preference has a polymeric matrix having a flexural modulus of at least 350,000 psi and a flexural strength of at least 12,000 psi, and an un-notched impact strength of at least 3.0 foot-pounds/inch. High strength dental polymeric material is preferably formed into dental products including full dentures, partial dentures, denture relines, night guards, crowns and bridges by polymerization of wax-like polymerizable dental material.
xe2x80x9cFlexural strength, and flexural modulusxe2x80x9d as used herein refers to results of testing according to ASTM D790 (1997). xe2x80x9cNotched impact strengthxe2x80x9d as used herein is also referred to as xe2x80x9cnotched Izod impact resistancexe2x80x9d and refers to results of testing according to ASTM D256 (1997). xe2x80x9cUn-notched impact strengthxe2x80x9d as used herein refers to results of testing according to ASTM D4812 (1993).
In the following examples, unless otherwise indicated, all parts and percentages are by weight; Lucirin TPO refers to 2,4,6-trimethylbenzoyldiphenylphosphine oxide made by BASF, and the visible light curing unit used was a TRIAD VLC visible light curing unit modified by adding a fifth light to provide about 30 milliwatts/cm2 of from 350 to 450 nm light.